Denture cleansers

ABSTRACT

IMPROVEMENTS ARE SET FORTH IN THE PRODUCTION OF DENTURE CLEANSERS CONTAINING INORGANIC PEROXY OXYGEN-LIBERATING COMPOUNDS WHICH WHEN ADDED TO WATER CAUSE EVOLUTION OF OXYGEN AND BUBBLING. MORE VIGOROUS BUBBLING AND HENCE MORE EFFICIENT CLEANSING OF ARTIFICAL DENTURES IS BROUGHT ABOUT BY THE INCLUSION OF CATALYSTS. A PARTICULARLY ADAPTABLE ACTIVATING MATERIAL IS ONE WHICH CONSISTS OF A HEAVY METAL CHELATE. THE SHELF-LIKE OF A CLEANSER OF THE TYPE DESCRIBED IS FOUND TO BE GREATLY LENGTHENED IF IT DOES NOT CONTAIN AN EXCESS OF THE HEAVY METAL COMPONENT. IT IS ALSO FOUND ADVANTAGEOUS TO AVOID AN EXCESS OF THE CHELATING AGENT. THUS IS IS PREFERRED TO PREPARE THE HEAVY METAL CHELATE WITH ITS COMPONENT PARTS IN STOICHIOMETRIC PROPORTIONS.

United States Patent 3,704,227 DENTURE CLEANSERS William H. Hill,Stamford, Conn., assignor to Peter, Strong & Company, Inc., New York,N.Y.

No Drawing. Continuation-impart of applications Ser. No. 210,584, July17, 1962, Ser. No. 507,705, Nov. 15, 1965, now Patent No. 3,372,125, andSer. No. 709,900, Mar. 4, 1968, now Patent No. 3,488,288. Thisapplication Nov. 20, 1969, Ser. No. 878,562

Int. Cl. Clld 7/54 US. Cl. 252-95 1 Claim ABSTRACT OF THE DISCLOSUREImprovements are set forth in the production of denture cleanserscontaining inorganic peroxy oxygen-liberating compounds which when addedto water cause evolution of oxygen and bubbling. More vigorous bubblingand hence more efficient cleansing of artificial dentures is broughtabout by the inclusion of catalysts. A particularly adaptable activatingmaterial is one which consists of a heavy metal chelate. The shelf-lifeof a cleanser of the type described is found to be greatly lengthened ifit does not contain an excess of the heavy metal component. It is alsofound advantageous to avoid an excess of the chelating agent. Thus it ispreferred to prepare the heavy metal chelate with its component parts instoichiometric proportions.

The present application is a continuation-in-part of copendingapplications Ser. No. 210,584 filed July 17, 1962 (now abandoned), Ser.No. 507,705 filed Nov. 15, 1965, now Pat. No. 3,372,125 issued Mar. 5,1968, and Ser. No. 709,900 filed Mar. 4, 1968, allowed July 14, 1969,now Pat. No. 3,488,288 issued Jan. 6, 1970.

The present invention relates to improvements in den ture cleansers andmethods of preparing the same, and more particularly to improvements incombinations of solid chemicals in mixtures that are highly useful whendispersed in liquid media for effectively and efficiently removing oraldeposits including, for instance, stains from food, tobacco, or othersources; 'mucin; food particles; tartar and calculus.

Mixtures of solid ingredients, such as those referred to in the aboveapplications, including one or more solid peroxidized compounds, providemeans whereby bubbling is effected in a liquid medium that serves inremoving oral deposits from removable dentures, It has been found thatcertain metal complexes may be included in cleansing mixtures containinga peroxidized compound to obtain a catalytically increased or controlledevolution of gas for more active bubbling without detracting fromdesirable charac-. teristics of such mixtures as denture cleansers. Inaccordance with this invention, It has been found that besidesinorganic, heavy metal complexes, certain organic acid materialscompounded with heavy metals, and ion-exchange materials compounded withheavy metals, which materials are described hereinbelow, have desirablecatalytic effects on oxygen evolution that is advantageously adaptablein cleansing operations in dentistry.

In the above application Ser. No. 210,584, stable, substantially dry,odorless, free-flowing, non-lumping, nondeliquescent, non-hygroscopic,compositions are disclosed for cleansing removable dentures and forremoving oral deposits therefrom. Solid ingredients are mixed togetherin particulate or finely divided form, preferably predominantlygranular, which remain free-flowing in a container, and which, whenadded to water, show no tendency to form a scum, and which provideclear, non-cloudy solutions in water.

Compositions are disclosed in the above application which containcombinations consisting essentially of a mixture of dipotassiumpersulfate, sodium perborate, and sodium carbonate, or mixtures ofsodium perborate, dipotassium persulfate, trisodium phosphate, andsodium carbonate. The following illustrate proportions in these mixturesthat give good results:

Parts by weight Dipotassium persulfate 5 to 25 Sodium perborate 10 to 50Sodium carbonate 10 to 50 Sodium perborate 10 to 50 Dipotassiumpersulfate 5 to 20 Trisodium phosphate 10 to 50 Sodium carbonate 10 to50 The sodium perborate can be the monohydrate or the tetrahydrate. Thesodium carbonate is preferably the monohydrate. The trisodium phosphatewhich is obtainable as fully hydrated with twelve molecules of water,should preferably be the monohydrate or the hemi-hydrate.

To the above may be added other ingredients. Sodium hexametaphosphate(NaPO may be included preferably in the glassy, crushed, unadjustedform. Other sodium metaphosphates are mentioned in the form of (HPOg)where n may be 2 or more. Other useful compounds are sodiumtripolyphosphate, pyrophosphates, sodium septaphosphate, or sodiummetasilicate.

Small proportions of a colouring and of a surfactant are addedadvantageously to a mix. Phenolphthtalein provides an attractive pinkcoloration when in proper concentrations. A surfactant, such as NacconolNR (sodium dodecyl benzene sulphonate) is included in proportions belowthat at which a foam or scum builds up when the product is mixed withwater. Other surfactants may be substituted, such as, for instance,Duponol C (sodium salts of sulfated fatty alcohols, such as, sodiumlauryl sulphate); non-ionic surfactants, such as Triton X"(Water-soluble iso-octyl phenoxy polyethoxy ethanol); Dowfax 9N9 (nonylphenol-ethylene oxide condensate having 9-10 moles of ethylene oxide).The surfactant should preferably be one of a reasonable stability inalkaline solutions, and one that is in a solid state is desirable forease of incorporation, though this is not essential.

A colloidal silica, also in small proportions, may be included tomaintain a mix in free-flowing state and to prevent lumping whensubjected to certain conditions. Cab- O-Sil is particularly preferredfor the present composition. When distributed in water with theformulations disclosed herein, a transparent, clear liquid is provided,since the particles are so tiny and transparent that they are invisibleor hardly visible to the naked eye in the concentrations used.

Cab-O-Sil is a colloidal, submicroscopic, pyrogenic silica prepared in ahot, gaseous environment by a vaporphase, flame hydrolysis, at hightemperature (around 1100 C.), of a silicon compound, such as silicontetrachloride. It is distinct from silica gel obtained by precipitationof silicic acid from an aqueous silicate solution, and hardenng of theprecipitate. Silica gel, thus formed, is internally porous, whereasCab-O-Sil" has an enormous external surface area and no internalporosity.

Cab-O-Sil" contains no water-soluble inorganic salts. It is of highchemical purity, low water content, and has a high degree of particleseparation. The properties and composition of a grade of Cab-O-Sil arelisted as follows:

Silica content (moisture-free)99.099.7% Free moisture (105 C. )0.21.5Ignition loss at 1000 C. (excluding moisture)0.2l.0% CaO, MgO--0.000%

Particle size range-0.0150.020 micron Sunfaoe area-175-20 sq.m./ gm.

Specific gravity2.1

Color--white Refractive index-1.46

pH (4% aqueous dispersion)3.54.2 Apparent bulk density-2.57.0lbs./cu.ft.

A finer grade of Cab-O-Sil has the above characteris tics but a particlesize range of 0.0070.010 micron, a surface area of substantially 325sq.m./gm., and a refractive index of 1.46.

The various grades of Cab-'O-Sil may be used interchangeably.

It is found that, except for the minor ingredients such as dye orcoloring, and the surfactant, it is best not to use the chemicals in afinely powdered form. It is advantageous and preferable to use them ingranular form with particle sizes preponderantly between substantiallyand 60 mesh and with a major proportion between 20 and 40 mesh. It isnot found objectionable when minor fractions are somewhat larger than 10mesh and as fine as 80 to 100 mesh.

The following examples designated as C and D serve to illustrate theinvention as disclosed in said application Ser. No. 210,594:

The following solid ingredients are mixed together in finely divided butgranular form preferably in the order listed. The preferred proportionsare given in parts by weight.

Sodium perborate 30 Dipotassium persulphate 20 Trisodium phosphate 30Sodium carbonate 20 Phenolphthalein 0.01 Nacconol NR (sodiumdodecylbenzene sulfonate) 0.04 Sodium hexametaphosphate 0.25 Cab-O-Sil"0.5-1.0

The following ingredients, in parts by weight, are finely granulated andmixed together:

Sodium perborate 40 Dipotassium persulfate 10 Trisodium phosphate 20Sodium carbonate 30 If desired, and for various purposes, enzymic orenzy: matic agents are advantageously included in the abovecompositions. Catalase in the proportion of about 0.001 to 0.1 percentby weight of the composition, as well as plantderived peroxidase serveto promote gassing. Protolytic enzymes assist in such compositions indissolving hardened mucin in refractory denture deposits. About 0.01 to0.02 percent by weight of the latter enzymes is effective. Pancreaticextracts and papain perform the latter function.

A half teaspoonful of the product of Example C in an eight ounce glassof water provides a solution with a pH of about 11.6 to 12. A solutionof the product of Example D. similarly prepared, has a pH of about 1.5to 12.

It has been discovered that there are metal complexes that can serve aseffective catalysts for more vigorous gassing, or increased rate ofevolution of gas, for use in denture cleanser products in a manner asstated and while retaining desirable characteristics mentioned. Amongthe complexes there are those having the general formula M,,[Fe(CN) (NO)wherein M is H, or where H is replaced by a variety of cations; x may be2 to 4; y may be 1 to 6; and 2 may be 0 to 1. Instead of iron, Fe, inthe anion part of the above formula, it is possible to have a metal suchas cobalt (CO), nickel (Ni), manganese (Mn), copper (CU) or others.Compounds particularly desirable for use as catalysts in cleanserproducts in dentistry, include salts of the following acids, namely,having the formulae listed below, and stable acids themselves:

Compounds that are in stable, solid form are preferred for purposes ofthe present invention. It is considered impractical or undesirable touse, in dental cleanser products, the compounds that are not stable ornot solid, or that are oxidizable or break down and give off HCN(hydrocyanic acid), or undesirable odors, or that introduce undesirableconstituents that are too volatile. The acid, bydroferrocyanic acid, forinstance, having the formula H,,[Fe(CN) is a stable, white solid that issoluble in water, ethanol, methanol, and other alcohols. It provides aclear solution while effectively increasing the rate of evolution of gasin an aqueous medium when used in association with a denture cleansercontaining a peroxidized compound. Its cost, however, is an item thatrenders it unattractive for use in a commercial dental cleanser product.

Hydrogen in the above acids is replaceable in part or completely bysodium, potassium, calcium, barium, and other alkali and alkaline earthmetals, singly, or in combinations thereof taking their valences intoaccount.

Any element or group of elements as a radical, that functions or canfunction as a cation, may replace the hydrogen in the above acidformulae. Such radicals are cited as NH V0, U0 M00 or W0 ions. From thestandpoint of the Periodic Table, the H is replaceable in part orcompletely by a variety of cations, or metals such as those in GroupsI-A, I-B, II-A, II-B, III-A, III-B, IV-A, IV-B, V-A, V-B, VI-A, VI-B,VII, and VIII.

Certain compounds mentioned for use as catalysts for purposes hereindescribed are generally referred to as cyanoferrates, or prussiates, andinclude materials such as the nitro prussides, for instance, Na; and

The cyanoferrate anions have desirable properties in that they elfectincreased gas evolution and do not decompose in an oxygen-producingmedium or in strong alkaline solutions. The water-soluble ferroferricyanides as well as the nitro prussides produce yellow solutionsand no solid precipitates in the presence of the above-described denturecleanser compositions. Furthermore, in their use as catalysts and afteran initial period of their presence for twenty-four hours in a cleansingsolution, further addition of denture cleanser material to the solutionproduces renewed accelerated active gassing.

Several commercial brands of Prussian blue provide very good gassingwith the above denture cleanser, as do Turnbulls blue freshly preparedfrom ferrous sulphate and potassium ferricyanide. A precipitate isformed with them and similar compounds because their cations appear inthe denture cleanser solution in solid form by double decomposition withactive components of the denture cleanser while the anions go intosolution as soluble prussiates.

Besides the above cyano ferrates, there are mentioned other compoundswhich involve complex 'iron cyanides of aliphatic bases, of aromaticbases, of heterocyclic bases, of alkaloids, and of other basiccompounds. In general, the organic ferrocyanides are also coloredcrystalline compounds which are usually infusible, insoluble; orslightly soluble in cold water, and relatively stable at roomtemperature. Ferrocyanides of diamino compounds tend to be relativelyunstable and more insoluble.

Among the cyanogen compounds, those with iron in the anion are to berecommended. Of the hexacyano compounds, the ferrocyanides, includingferrocyanic acid, H [Fe(CN)e], are preferred over the ferricyanides,including ferricyanic acid, H;.;[Fe(CN) for use in the denture cleanserproducts. The ferrocyanides are more stable and cheaper. Theferricyanides are generally less stable and more expensive.Incidentally, in the case of cobalt, the reverse is true as tostability, cobalto cyano complexes being less stable than the cobalti.

The most desirable hexacyano compounds are the soluble alkali prussiatesincluding sodium and potassium ferrocyanides. These form substantiallypermanent, clear solutions with a pleasing yellow color, in the presenceof the required proportion of the denture cleanser material in water.Ammonium ferrocyanide is mentioned but its liberation of ammonia is notalways desirable.

The prussiates vary considerably as to solubility. Both the soluble andinsoluble cyano ferrates are generally equally effective catalytically.The insoluble ones chemically react with alkaline solution of a ceansermix in such a fashion that a soluble prussiate is formed from theanionic portion of the insoluble catalyst and the alkali components ofthe cleanser mix, soluble ferroor ferricyanide being formed depending onthe derivation and origin of the insoluble catalyst. For instance, if ablue, solid catalyst is made from a Water-soluble ferrocyanide, then aferrocyanide is formed in the cleanser solution. If an insoluble blue ismade from a soluble ferricyanide, then a water-soluble ferricyanide isformed by reaction with the cleanser solution. In either case, thepolyvalent metal comprising the cation of the insoluble blue is splitoff in the cleanser solution with formation of the correspondinghydroxide, carbonate, phosphate, or mixture thereof, depending on whatanions are represented in the denture cleanser solution.

Among the water-soluble prussiates, calcium ferrovyanide, Ca [Fe(CN)provides good gassing; barium ferrocyanide, Ba [Fe(CN) provides veryexcellent gassing; calcium potassium ferrocyanide, CaK [Fe(CN) providesexcellent gassing, but in each case a flocculent precipitate keepsrising in the cleanser solution during gassing.

Where desired gassing and other results are obtainable, but turbidity,or coudiness is found objectionable, as in the use of prussiates as thecatalysts and in which H of the acids is partially or wholly replaced bycalcium or other alkaline earth or other polyvalent metal, for example,CaK [Fe(CN) with which only slightly turbidity in a cleanser solution islikely, such turbidity is lessened or prevented by appropriatelychanging the cleanser formulation to include a sequestering agent suchas hexametaphosphate, tripolyphosphate, or pyrophosphate, or even EDTA(ethylenediamine tetraacetic acid) or related chelating agents.

-It is advantageous to use catalysts, or catalyst mixtures, that havethe least amount of water of crystallization. This is also preferred asto other constituents of the cleanser. The reasons are mainly thatcaking of the cleanser product is prevented, and premature catalysis orlocal decomposition is substantially avoided, leading to increasedshelflife of the denture cleanser product. In general, the insolubleprussiates are advantageous in this respect because they are usuallyfree of water of crystallization.

Solid cleanser mixes of the present invention contain solid catalyststhat may be soluble or insoluble in water.

When any of such solid mixes is introduced into water for cleansing adenture, the water-soluble constituents, including a peroxidizedcompound such as perborate or persulfate or percarbonate, proceed to gointo solution and the bubbling or gassing commences. While the catalystcontinues to be in a solid state the catalytic effect is most pronouncedand the evolution of gas is most vigorous for a given catalyst. Suchevolution takes place most vigorously at the points of contact betweenthe solid particles and the liquid. Around each solid particle ofcatalyst, the action is localized and there is a zone or layer that hasthe highest concentration of catalytic material in a given system, andtherefore the catalytic effect is greatest in such zone or layer closestto the catalyst surfaces, thereby providing a lively local gas evolutionwhich in general prevents caking of the soluble constituents of thecleanser in the cleansing operation. These conditions continue so longas prussiate anion or catalytic material is still contained in the solidparticles of catalyst in the cleansing solution. The bubbling continuesto be most vigorous in the initial stage while the catalyst is inprocess of dissolving. After solid particles of a catalyst are no longerpresent, the catalytic effect is lessened, and bubbling or gassingcontinues but it is less vigorous for a period and finally ceases whenall the peroxidized material is exhausted. In other words, a gradualdiffusion takes place, gassing is initially accelerated, and utimatelybecomes more uniform and continuous.

With certain mixed catalysts, a cyalno ferrate or metal cyanogen complexof low solubility may be mixed with one of higher solubility so that amore highly vigorous evolution of gas is initially obtained. This founduseful especially in tablets containing the ingredients of a denturecleanser including a peroxidized compound plus a catalyst mixture whichwill cause an initial gassing of sufficient vigor to disrupt ordisintegrate such tablets when placed in water. In tablets, this canalso be brought about by mixing with a ferrocyanide catalyst that isincluded in a dental cleanser solid mix, a small proportion of complexesof EDTA salts with a heavy metal (iron, manganese, copper, or cobalt),or a cobaltic nitrite, or a cobalti cyanide. The initial catalyticeffect desired may be predetermined by the nature of a catalyst or bythe ratio of a more active catalyst to a less active catalyst in acatalyst mixture.

A single catalyst compound may be mixed with a denture cleanercomposition in the proportion by weight of substantially 0.1 to 1% (orup to 5%) of the total cleanser composition. The total proportion of theabove-described catalyst mixture, and other catalysts herein described,on the other hand, may be as low as 0.01 to 0.2 percent of the totalcleanser mixture by weight. The size of the soluble catalyst particlesranges preferably from 20 to 60 mesh, or even 20 to mesh, while thewater-insoluble catalysts, being often colloidal in nature, may compriseparticle sizes as small as several microns or a fraction of a micron.

The following examples serve to illustrate catalytically affectedcleansers:

When the above mixture is added to about 8 ounces of warm water in theamount of about /2 teaspoon, the water is at first colored violet, thenit changes it changes to magenta, then to pink, and finally becomescolorless. A very small amount of pale tan flocculent solid appearseventually in the solution. The gas evolution in the cleansing solutionis excellent.

EXAMPLE 2 Parts by weight Sodium perborate 30 Potassium persulfate 20Trisodium phosphate 30 Sodium carbonate 20 Phenolphthalein 0.01 NacconolNR 0.2 Sodium hexametaphosphate 0.25 Cab-O-Sil n 0.5 Potassiumferricyanide 0.5

One half teaspoon of the above mixture is added to about 8 ounces ofwarm water (approximately 110 F.). The water is colored a rose pink inthe beginning, then the color changes to a lighter pink, and eventuallythe solution becomes clear and faintly yellow. The gas evolution is veryexcellent.

EXAMPLE 3 A formulation similar to that in Example 1 is provided exceptthat the Prussian Blue as catalyst is replaced by 1 part by weight ofsodium nitroprusside. The initial color of the solution after additionof the cleanser composition is an orange pink which gradually turns to apinkish tan and eventually to a clear, intense yellow. The gas evolutionis extremely vigorous, especially in the beginnmg.

The solution, after addition of /2 teaspoonful of the above mixture toabout 8 ounces of Warm water becomes a strong pink which eventually intime fades out to colorless. The gassing is very good in the beginningand especially when there is still solid salt in the container adjacentto the bottom.

EXAMPLE 5 Parts by weight Trisodium phosphate 20 Sodiumtripoly-phosphate 20 Sodium perborate 20 Sodium carbonate 20 Potassiumpersulfate 20 Phenolphthalein 0.02 Duponol C 0.5 Sodiumhexametaphosphate 0.5 Cab-O-Sil 0.5

Calcium potassium ferrocyanide CaK [Fe(CN) On addition of /2 teaspoon ofthe above mixture to warm water, the solution turns an intensive pink,and very excellent gas evolution starts immediately. The gas bubbles arevery fine and a foam layer appears at the surface of the liquid, becauseof the relatively high concentration of the surfactant. Occasionalstirring is helpful in breaking up the foam layer and in expeditingclarification of the liquid. Within 20 minutes the pink color disappearsand the solution is crystal clear.

8. EXAMPLE 6 Parts by weight Trisodium phosphate 20 Sodiumhexametaphosphate (adjusted) 20 Sodium perborate 20 Sodium carbonate 20Potassium persulfate 20 Phenolphthalein 0.02 Duponol C 0.1 Cab-O-Sil 0.5Calcium potassium ferrocyanide 0.1

The same observations are made in this example as in Example 5, exceptthat gas evolution is somewhat less vigorous and the foam layer is lessdense and less in volume than that observed in Example 5.

It has been found that heavy metal compounds of a chelating aminopolycarboxylic acid, and heavy metal compounds of :a cation exchangeresin can be highly effectively employed as the activating agents in thepresent cleanser product.

Products such as heavy metals in chelated form and thus very littleionized, as in a heavy metal salt of a noncyclic amino polycarboxylicacid, can be obtained very readily without water of crystallization.They are much less likely to cause premature oxygen release in denturecleanser compositions and thus provide better shelf-life for solidcleansers. The heavy metals compounded with the amino polycarboxylicacids, such as ethylenediamine tetraacetic acid (known as EDTA, andsold, for instance, under the name Sequestrene), nitrilotriacetic acid,diethylene-triamine pentaacetic acid, hydroxy-ethyl ethylenediaminetriacetic acid, hydroxyethylaminodiacetic acid, methylaminodiaceticacid, aminotriacetic acid and others function as activating agents insolution and therefore as homogeneous catalysts. Compounds such assodium-cobalt EDTA, sodium-copper EDTA, sodium-nickel EDTA,sodium-ferric EDTA, sodium-ferrous EDTA, and sodiummanganese EDTA, monosodium ferrous hydroxyethyl ethylene diamine triacetate, and mono sodiumcuprous hydroxyethyl ethylene diamine triacetate, when substituted forthe metal complexes listed as catalysts in the above Examples 1 to 6, inthe same proportions or in catalytically effective amounts up to 5%,provide varying degrees of gassing. The cobalt, copper and ferric metalsso compounded give excellent gassing. The gassing with the other metalsvaries from fair with nickel to mostly very good with ferrous andmanganese chelates.

Importance is placed on the use of heavy metal chelates which areprepared with a chelating agent and a heavy metal salt in stoichiometricproportions without an excess of either the chelating agent or the heavymetal salt. Any metal salt, such as copper sulfate, iron sulfate,manganese sulfate, etc., which is not properly chelated, is apt to beprematurely reactive in the denture cleanser solid mix containing anoxygen-generating ingredient, and this results in poor shelf-life of thecleanser composition. When the chelates are made in appropriatestoichiometric proportions, such metal salts are absent. When a denturecleanser composition containing a heavy metal chelate prepared as notedabove, is added to water for the purpose of cleaning removable dentures,the initial gassing is usually relatively slow, but in a very short timethe gassing increases rapidly to a desired high level, and the gassingis as vigorous as it would be when unchelated metal is present.

The presence of an excess of a chelating agent in denture cleansercompositions described herein is disadvantageous in that the gassingremains at a minimal rate until the excess is destroyed by the oxidizingaction of the denture cleanser bath. Excesses of the chelating agent,particularly when large, suppress the formation of heavy metal cationsthat catalyze the gassing action, and the desired increased,undiminished bubbling for a combined bleaching, cleaning and fooddislodging action is not obtained.

The cation exchange resin materials compounded with the above heavymetals have an excellent activating effect on the aforesaid cleansers inWater, which can be adapted to the control of gassing by varying theparticle size of the salts. The salts are insoluble in Water and serveas heterogeneous catalysts. They are obtainable finely divided (100 to200 mesh and to 400 to 600 mesh) or in granules to 50 mesh). Variousmesh ranges are usable including that of a so-called micro powder.Catalysis is less vigorous with the coarser grades. When the dryparticles are diflicut to wet in Water, a rinse with a dilute solutionof a cationic, anionic, or non-ionic surfactant, overcomes suchdifiiculty.

There are two classes of cation exchange resins, both being suitable inpreparing the activating agents as heavy metal compounds, namely, thestrong acid resins and the weakly acid resins.

The strongly acidic cation exchange resins, such as the polystyrenenuclear sulfonic acid type, are mostly those in which divinyl benzene iscross-linked with polystyrene sulfonic acid. The weakly acidic cationexchange resins are those of the carboxylic acid type such as thoseprepared by copolymerization of methacrylic acid and divinyl-benzene.When used in a hydrogen or a sodium cycle operation, they may becompounded, in a Wellknown ion exchange column, or in a batch operation,with any of the aforesaid heavy metals. It is also possible to compounda heavy metal EDTA salt with an anion exchange resin (such as a basic,quaternary amine-type anion exchange resin), because in such a chelatedform the metals are anionic and thus react with anion exchange resins.These various resins are produced under the name Amberlite (by Rohm &Haas Company), DOWEX (Dow Chemical Co.), and others. In numerous gassingtests in which the above agents were substituted for the activatingagent in Examples 1 to 6 in substantially the same proportions, or addedto compositions A, B, C or D above, the gassing was good to veryexcellent.

Other material having cation exchange capacity is useful for the abovepurpose, as for instance, various natural and synthetic zeolites.

A denture to be cleaned is introduced in a water solution serving as thecleanser and is permitted to remain therein for a relatively short time.The denture is removed and washed with fresh water and inserted in themouth. The cleanser is distinctive in that no after-taste is noticeableon a denture so treated. The color from the indicator usually fadeswithin twenty-four hours and this serves as a warning that the solutionhas been used and that it is no longer sufliciently fresh for reuse.Certain of the ingredients, such as the perborates, act as strongdisinfectants, and the treatment of dentures as described 10 tends tocounteract denture breath that develops when the dentures are in use.

In the use of the above-described products in cleansing dentures, adenture to be cleansed may be left in a solution of the selectedcomposition for as long as desired without injury to the denture.One-half hour to one hour or less is usually suflicient to obtainthorough cleansing. Brushing of a denture with the solution is notnecessary and should be avoided where certain plastics used in a denturestructure are likely to be injured thereby. Application of a solidcleanser or of a solution thereof and rubbing of the denture by hand aregenerally sufficient for softening and removing scaly debris in the mostdifiicult instances.

What is claimed is:

1. A denture cleanser consisting of a particulate, solid mix having awater-soluble, inorganic peroxy oxygen-liberating compound adapted toevolve gas bubbles upon addition of said mix to an aqueous medium forcleaning a denture, and a heavy metal chelate, the said chelateconsisting of an activating heavy metal selected from a group consistingof manganese, iron, copper, cobalt, and nickel, chemically combined witha chelating compound in substantially stoichiometric proportions, thesaid chelating compound selected from a group consisting ofethylenediamine tetraacetic acid, diethylenetriamine pentaacetic acid,hydroxy-ethyl ethylene-diamine triacetic acid,hydroxyethylamino-diacetic acid, methylaminodiacetic acid, andaminotriacetic acid, and the said mix being substantially free from anexcess of the said heavy metal over its stoichiometric proportion, andsubstantially free from an excess of the said chelating compound overits stoichiometric proportion.

References Cited UNITED STATES PATENTS 3,211,658 10/1965 Hirtz et al202---99 3,337,466 8/1967 Puetzer et al. 20 299 3,398,096 8/1968 Das202-99 3,156,654 11/1964 Konecny et al. 202-99 FOREIGN PATENTS 984,4592/ 1925 Great Britain 202-99 OTHER REFERENCES Sequestrene, Geigy Ind.Chem., 1952, pp. 5, 21, 36, and 48 relied on.

MAYER WEINBLA'IT, Primary Examiner U.S. Cl. X.R.

